1. Field of the Invention
The present invention relates to an optical module that provides an optical device installing a semiconductor optical device and an optical receptacle for receiving an optical ferrule provided in an end of an external optical fiber.
2. Related Prior Art
An optical module applicable to the optical communication system generally comprises an optical device that installs a semiconductor light-emitting device, typically a laser diode (hereafter denoted as LD), or a semiconductor light-receiving device such as photodiode (hereafter denoted as PD), and an optical receptacle to receive an optical ferrule provided in the end of the external fiber to align the optical ferrule optically with the LD or the PD in the optical device.
As the operational frequency of the optical module mentioned above becomes higher, an electro-magnetic interference (EMI) due to the LD or the PD in the optical device may be easily emitted from the optical device. The external EMI noise due to the system installing the optical device, typically an optical transceiver, may also easily invade into the optical device. The optical receptacle combined with the optical device generally has a metal body to shield the optical device when the optical module is set in the system.
A Japanese Patent Application published as JP-2006-119577A, has disclosed one type of an optical module, which is illustrated in FIG. 4A, where an optical unit 100 that installs a semiconductor device 3 such as LD and an optical receptacle 200 that receives an external optical fiber. In the optical module shown in FIG. 4A, the insulating spacer 11 set into a spot 8b of the stub holder 8 and also into a bore of the sleeve cover 9 electrically isolates the metal stab holder 8 coming in contact with the optical device 100 from metal sleeve cover 9 to be contact with an external optical connector.
A United States patent, U.S. Pat. No. 7,217,042 has disclosed another optical module whose arrangement is schematically illustrated in FIG. 4B. In this optical module, an insulating cylindrical ring 15 set between the upper and lower metal rings, 14 and 16, to isolate the optical device 1 electrically from the optical receptacle 2.
The prior optical modules shown in FIGS. 4A and 4B electrically isolate the optical device that installs an LD or a PD from the optical receptacle for receiving the external optical connector. This arrangement may shield the optical device from the external radiation noise and may protect the optical device from an external surge. However, the arrangement to isolate the optical device from the outside appeared in these prior arts have a complex structure. In the former prior art, the spacer 11 which is set between the stub holder 8 and the sleeve cover 9 always receives a compressive stress from both members. While, in the other prior art, the insulating ring 15 and two metal rings, 14 and 16, put the insulating ring 15 therebetween are press-fitted to each other; that is, the insulating ring 15 is press-fitted into the upper ring, the lower ring 16 is press-fitted into the insulating ring 15, then the optical device 7 is welded with the lower ring 16 and the bush in the sleeve member 2 is welded with the upper ring 14. Moreover, the latter arrangement appeared in the U.S. Pat. No. 7,217,042 has an essential restriction that the insulating ring 15 is necessary to be formed in thin.
The present invention is to provide an optical module that may electrically isolate the optical device from the optical receptacle by a simple arrangement, accordingly, to provide a cost-effective optical module.